Typically, light-emitting devices, which are used outdoors, are exemplified by electronic display substrates using neon, cold cathode lamps (CCLs), or light-emitting diodes (LEDs). Also, examples of light-emitting devices, which are used indoors, include external electrode fluorescent lamps (EEFLs), cold cathode fluorescent lamps (CCFLs), and LED boards.
Neon lights and CCLs are problematic because they adopt high-voltage power supplies and thus consume a large amount of power, entail the risk of electric shock and fire, and furthermore have short lifetimes. Meanwhile, EEFLs and CCFLs are difficult to use outdoors because they operate at high frequency and have low illuminance and short lifetimes.
For electronic display substrates using LEDs, the rear of the light-emitting surface is blocked by a cover due to the processing of black film or wires on the rear side, so that only the unidirectional emission of light is possible.
Recently, light-emitting devices have come to be utilized as advertisement boards, rather than simply being used as illuminators, and are also widely employed for aesthetic purposes in the field of interior design.
In the aforementioned light-emitting devices, however, limitations are imposed on the sizes of lamps or stands for supporting the light-emitting devices, making it difficult to impart aesthetic appearances.
Hence, in order to attain aesthetic appearances, conductive substrates are typically devised, in which circuit elements are attached to electrodes and are then controlled using a controller to emit light, thus displaying text or images from the electrodes and also showing mobile images. Such conductive substrates are configured such that circuit elements are wired to the electrodes, and include circuit elements having two electrodes, three electrodes, and four electrodes.
In this regard, a conventional conductive substrate is disclosed in Korean Patent Application Publication No. 2008-0101250 (Laid-open date: Nov. 11, 2008). The conventional conductive substrate is configured such that circuit elements having two to four electrodes are bonded to the electrodes of a conductive substrate using a coating process with a conductive adhesive.
In the conventional conductive substrate, individual wires formed by etching of electrodes have to be electrically insulated from each other, but the adhesive applied to bond the circuit elements spreads depending on the amount and position thereof, thus causing short circuits due to contact between conductive adhesives, low electrical conductivity due to contact between conductive and non-conductive adhesives, and flowing of the adhesive out of the areas to which circuit elements are bonded, undesirably resulting in poor aesthetic appearances.